Better than being the “best-kept secret” road race in America is the secret getting out.

The annual Enmark Savannah River Bridge Run may be Savannah’s “hometown race” and a “city signature event,” as race director Robert Espinoza has called it, but it draws beyond local borders and bursts whatever seams organizers place on entry numbers.

This Saturday morning, Savannahians and out-of-towners will run, walk and, yes, perhaps even crawl (as the slogan says) across the Talmadge Bridge in greater numbers than ever before.

Final registration, which runs from 9 a.m. to 7 p.m. today at the event’s Expo at Savannah International Trade and Convention Center, will be capped at a combined 6,500 entries for the 5K, 10K and Double Pump (both races back-to-back).

That’s 500 more than last year, 1,500 more than the 2010 cap, 2,000 more than 2009 and, well, you get the idea.

It’s a trend that hasn’t gone out of fashion since Espinoza became the race director and Savannah-based Enmark became the title sponsor in 2002.

The event got a boost of free publicity and national exposure in December 2006, when it was the race of the month in Runner’s World magazine, and was recommended again in 2007. Bart Yasso, who made those picks as chief running officer of the magazine, described the Bridge Run as “the best-kept secret” on a list of his 23 favorite “must-do races near and abroad” in his 2008 book.

Have Mercer

Espinoza took over a 10K race which had been run annually in the heat of May and was marred in 2001 by a malfunction with the timing system, so there were no official times for the 993 finishers.

He met with Jim Mercer, then Enmark’s vice president and general manager and an avid runner. Mercer had a vision of something bigger than the 400 to 900 runners who showed up during the previous decade of races.

“That’s when all the plans went into place,” Espinoza said. “We started making it more about being an event than just a run or a walk, and here we are.”

Where the Bridge Run is on the calendar is the first Saturday in December, a change Espinoza made the first year, resulting in about 900 runners for a cold morning. But he knew it was the right move.

“May sounds pretty. It sounds like it’s going to be good and nice,” he said. “When you talk about running and it might be 80 to 85 degrees with 90 percent humidity, there’s no way to function.”

Runners now embrace the conditions, putting on layers for the start and shedding them as necessary as they climb and descend the bridge and the sun burns off the morning fog.

The Talmadge, of course, is the main attraction in the South’s toughest bridge run, in its director’s opinion. The tallest hill in flat Savannah will be traversed once by the 5K racers, twice by the 10K contingent and three times by those gluttons for punishment, the Double Pump entrants.

(The name “Double Pump,” by the way, struck Espinoza in a eureka moment about five years ago as he was running the bridge and wanted to better link the 5K and 10K races, with Enmark gas stations as a theme.)

One of those Double Pumpers, Dan Pavlin, said it’s the only time all year he can run across the bridge.

“For me, it’s always a fun race,” said Pavlin, 30, of Richmond Hill. “You expect the bridge to be really difficult but it’s actually more interesting and engaging mentally than most races. Everybody has a good time. It’s run professionally from start to finish. It’s got a great environment. It’s also a challenge.”

The difficulty posed by bridge runs is intriguing to a certain demographic of runners, said Savannah’s Robert Santoro, who won the marquee 10K race in 2009 and 2010 — the only two times he has entered the Bridge Run.

“Of course, you have the local people who run it year in and year out. It’s an accomplishment,” said Santoro, who had signed up for the 2011 Double Pump but was out of town, and expects to miss Saturday’s race because of work obligations.

The Bridge Run is attractive because of the challenge and its great organization, Santoro said.

“It’s important to the runners,” he said. “There’s a big difference between a well-organized and poorly organized race.”

Runners want the course secured and clearly marked, the timing system to work without complications, food and beverages ready for their replenishment and a nice place to congregate for awards.

“There are many races I’ve done, I’ve said, ‘I’m not coming back to this,’ ” said Levi Sybert, the Richmond Hill High School cross country coach.

He keeps coming back to the Bridge Run.

“Everything is on time,” said Sybert, who has finished second in the 5K the past three years. “Robert (Espinoza) does a wonderful job in everything he does.”

Twists and turns

Espinoza and his team have experimented with the format and course over the years. They no longer award prize money in the 10K — which lured elite racers to Savannah but gave little motivation to most runners — instead putting more funds toward the event and charities.

Espinoza credits city officials and services, the Savannah Area Chamber of Commerce and the Greater Savannah Sports Council for embracing the event and its possibilities.

Having Michelob Ultra as title sponsor of the postrace party doesn’t hurt.

“You have to make it special,” Espinoza said of why some races grow and others become stagnant or regress in popularity.

“A lot of it has to do with creativity. There are so many 5Ks in town now. There are can only be so many. You have to have something that has a twist to it.”

Twists like a three trips across the bridge, or a mud run, or a combination of races adding up to a marathon on Tybee Island. And don’t forget the postrace party.

“The last thing they remember is how much fun they had after they ran,” Espinoza said. “If you have a run and give people a bottle of water and a piece of orange and say thank you for coming, they probably won’t be back the following year.”

He quickly added that some races don’t have the budget and save money where they can, and that in tough times, people don’t enter as many races.

But when it comes to running the bridge, “it’s just one of those events you have to do because it’s a city signature event. What makes it special, too, is it’s the one time you can run on the bridge legally.”

The running community continues to grow. Whether they are running, jogging, walking or going to the gym, they are moving and that pleases Espinoza.

He said the old “Slow-vannah” criticism is a positive in his world.

“Years ago, there was the running boom and we hadn’t reached it yet. We’re in our running boom now,” he said. “The city is buzzing and they’re running and they’re moving and we’ve only just begun.”

GROWTH SPURT

Since Enmark became the title sponsor and Robert Espinoza the race director in 2002, the Savannah River Bridge Run has grown from under 1,000 entries to more than 6,100 last year (according to organizers):